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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Simulations of Mach 0.8 Transonic Truss-Braced Wing Aircraft Aerodynamics at High Angles of Attack

This paper presents numerical simulations of the Mach 0.8 Transonic Truss-Braced Wing (TTBW) aircraft at high angle of attack using CFD solver FUN3D. Three different approaches - steady Reynolds Averaged Navier-Stokes (RANS), Unsteady Reynolds Averaged Navier-Stokes (URANS), and Delayed Detached Eddy Simulation (DDES) are used to simulation the TTBW aircraft at Mach number 0.8 and altitude 40, 000 ft. The pitch break phenomenon is observed at this flight condition. The simulation results show that the pitch break angle of attack occurs at 2.75˚ by DDES, 2.81◦ by URANS, and 2.89˚ by RANS. The DDES unsteady pressure begins to grow at angle of attack of 3.5˚, which might indicate the buffet onset, and rises one order of magnitude larger at angle of attack of 4.0˚. However, the URANS unsteady pressure begins to grow at angle of attack of 4.0˚. Both unsteady simulation results show the pitch break occurs before buffet onset.

TTBW↗
NASA NTRSDate not supplied

Simplified Applied Loads of a Transonic Truss-Braced Wing Derived from Computational Fluid Dynamics

The transonic truss-braced wing (TTBW) concept is under consideration by the NASA Advanced Air Transport Technology (AATT) project due to its potential to reduce fuel consumption of transport aircraft. To properly evaluate the TTBW concept, detailed structural modeling and subsequent test planning is underway, which requires a simplified set of discrete applied loads that simulate the distributed aerodynamic pressures. Given the unique architecture of the TTBW and its intended operation in the transonic regime, computational fluid dynamics (CFD) is the ideal approach to employ to ensure the aerodynamics of this configuration are sufficiently captured. To convert aerodynamic results into input for structural models, application of a data transfer tool, Discrete Data Transfer Between Dissimilar Meshes (DDTBDM), is presented to resolve aerodynamic pressures from CFD into single load vectors at hardpoints along both the wing and the strut. Evaluation of mapping the aerodynamic forces to hardpoints at rib and spar intersections in a structural model is performed, and the results are also compared with a linear static aeroelastic analysis. The structural responses indicate that distributing forces along only the wing and strut forward spars is insufficient for simulating the distributed aerodynamic loads. Adding moments along the forward spars improved the global response of the wing, but the point moments created unrealistic local rotations within the structure. When distributing loads along both the forward and aft spars of the wing and strut, the global response was less sensitive to the inclusion of point moments, which indicated the arrangement of point forces alone was sufficient input for structural design work and testing and provided a more continuous loading profile.

Finite Element↗
NASA NTRSDate not supplied

Multidisciplinary Optimization of A Transonic Truss-Braced Wing Aircraft Using Aviary

The continuous push to decrease fuel burn of single-aisle commercial aircraft has led to interest in a Transonic Truss-Braced Wing (TTBW) concept vehicle. Sporting high-slung wings that are long and slender to increase aerodynamic efficiency, a TTBW can also accommodate higher-bypass turbine engines. The combination of these two changes potentially leads to an overall decrease in fuel consumption. In this paper, a TTBW concept vehicle is assembled in the Aviary open-source tool for conceptual aircraft design. The conceptual-level aerodynamics and propulsion systems that come prepackaged with Aviary are replaced with higher-fidelity vortex lattice method for aerodynamics (VSPAERO) and a one-dimensional cycle analysis tool for propulsion (pyCycle). The vehicle is then optimized to minimize fuel burn for a representative commercial mission. Design parameters for the vehicle include the electrified turbine size, the size of the electric motors which are used for takeoff and climb assist, and battery capacity. The TTBW concept vehicle presented in this paper represents the first application of Aviary to an aircraft design problem.

Optimization↗
NASA NTRSDate not supplied

Aeroelastic Simulation of Transonic Truss-Braced Wing Aircraft for Flight Dynamic Stability Analysis

This paper presents aeroelastic simulation of the Mach 0.8 Transonic Truss-Braced Wing (TTBW) aeroelastic model using CFD solver FUN3D for the flight dynamic and control stability analysis. A jig twist optimization is performed to obtain a flight optimized jig twist for the flexible Mach 0.8 TTBW model. The developed aeroelastic model steady-state stability derivatives with respect to the angle of attack, angle of sideslip, and airspeed are calculated with perturbations in the angle of attack, angle of sideslip, and Mach number, respectively. A series of unsteady simulations is conducted for the developed aeroelastic model in pitch oscillation at various reduced frequencies. The dynamic stability derivatives are estimated using a frequency domain estimation method. The control derivatives of the elevator, rudder, and ailerons of the developed aeroelastic model are estimated for control stability analysis.

TTBW↗
NASA NTRSDate not supplied

Simplified Applied Loads of a Transonic Truss-Braced Wing Derived from Computational Fluid Dynamic

The transonic truss-braced wing (TTBW) concept is under consideration by the NASA Advanced Air Transport Technology (AATT) project due to its potential to reduce fuel consumption of transport aircraft. To properly evaluate the TTBW concept, detailed structural modeling and subsequent test planning is underway, which requires a simplified set of discrete applied loads that simulate the distributed aerodynamic pressures. Given the unique architecture of the TTBW and its intended operation in the transonic regime, computational fluid dynamics (CFD) is the ideal approach to employ to ensure the aerodynamics of this configuration are sufficiently captured. To convert aerodynamic results into input for structural models, application of a data transfer tool, Discrete Data Transfer Between Dissimilar Meshes (DDTBDM), is presented to resolve aerodynamic pressures from CFD into single load vectors at hardpoints along both the wing and the strut. Evaluation of mapping the aerodynamic forces to hardpoints at rib and spar intersections in a structural model is performed, and the results are also compared with a linear static aeroelastic analysis. The structural responses indicate that distributing forces along only the wing and strut forward spars is insufficient for simulating the distributed aerodynamic loads. Adding moments along the forward spars improved the global response of the wing, but the point moments created unrealistic local rotations within the structure. When distributing loads along both the forward and aft spars of the wing and strut, the global response was less sensitive to the inclusion of point moments, which indicated the arrangement of point forces alone was sufficient input for structural design work and testing and provided a more continuous loading profile.

Finite Element↗
NASA NTRSDate not supplied

Simulating Transonic Buffet Aerodynamics for the Boeing Transonic Truss-Braced Wing Aircraft

The flow past the Boeing Transonic Truss-Braced Wing (TTBW) aircraft is simulated with a Hybrid Reynolds-Averaged Navier Stokes Large-Eddy Simulations (HRLES) turbulence modeling approach to study transonic buffet onset and evaluate the predictive capability of the numerical approach. All simulations used structured overset curvilinear grids for the free-air configuration, with all simulations performed using the Launch, Ascent, and Vehicle Aerodynamics (LAVA) computational framework. Aerodynamic loads and surface pressure obtained from the HRLES solutions are compared to results from unsteady RANS (URANS) and experiments conducted at NASA Ames 11-by 11-Foot Transonic Wind Tunnel. Overall good agreement is obtained in the predicted loads and surface pressure. Unsteady pressure data from HRLES and URANS simulations is utilized to compute power spectral density (PSD) to predict transonic buffet onset and compared to the Kulite data obtained from the experiment. Comparisons of the PSD spectrum also show reasonable agreement with the wind tunnel data, with HRLES and URANS predicting buffet onset at a slightly earlier angle-of-attack than the experiment.

AATT↗
NASA NTRSDate not supplied

Nonlinear Dynamic Control Derivative Analysis for Aircraft with Application to Transonic Truss-Braced Wing

This paper presents the development of a nonlinear dynamic control derivative estimation method. A nonlinear aerodynamic model is developed to account for the effects of large control surface deflections on aircraft aerodynamic forces and moments. A series of unsteady RANS CFD simulations is performed to simulate the control surface oscillations at various reduced frequencies. The time-domain data are transformed into the frequency-domain data by a Fourier series analysis. Transfer functions of the dynamic control derivatives are then estimated by a frequency-domain regression. The method is applied to the Transonic Truss-Braced Wing (TTBW) to estimate the dynamic control derivatives for the elevator, aileron, and rudder.

Aircraft Control Derivatives↗
NASA NTRSDate not supplied

Multidisciplinary Optimization of a Transonic Truss Braced Wing Aircraft with Hybrid-Electric Propulsion

Next generation aircraft concepts have subsystems that are increasingly inter-connected. This necessitates advanced design tools using gradient based optimization to properly account for strong subsystem coupling in these aircraft. Additionally, these design tools require accurate modeling capability to support the increased interest in electrified propulsion. Design studies for these aircraft must consider the trade-offs between electric propulsion and turbojet engines at all points in the flight envelope to determine the optimal balance between propulsion options. This paper describes the development of an electric propulsion subsystem model designed to work within Aviary - an open source aircraft design tool. We will demonstrate the electric propulsion model operating with Aviary by showing results from an optimized Transonic Truss-Braced Wing (TTBW) concept using assisted electric propulsion during climb. First, we present results with and without electrification to show the overall system impacts of hybrid electric propulsion during climb. We also present two distinct battery models compatible with this optimization framework, and compare results using both. Next, we ran the same problem using a slightly different cell type, and demonstrate a considerable change in the result. Finally, we vary the cell energy density of the batteries, and provide an illustrative trend for the system-level impact for improving cell technology.

optimization↗
NASA NTRSDate not supplied

Aeropropulsive Assessment of a BLI Tail-Cone Thruster Propulsion System for the NASA Common Research Model and a Transonic Truss-Braced Wing Configuration

This paper presents an investigation into the potential benefits of a boundary layer ingestion(BLI) aft fuselage propulsion system, or tail-cone thruster (TCT), when applied to two transport category aircraft: a conventional tube-and-wing configuration based on the NASA Common Research Model (CRM) and a transonic truss-braced wing (TTBW) configuration. Through the ingestion of low-momentum flow developed over the airframe of an aircraft, the TCT propulsion system technology can reduce overall power consumption and hence fuel burn and emissions. However, an accurate assessment of this potential requires the application of high-fidelity analysis tools that can capture the relevant propulsion-airframe integration effects, at least to first order. Toward this end, the present study employs aeropropulsive analysis tools based on the Reynolds-averaged Navier-Stokes equations to estimate the power savings coefficient, measured relative to equivalent non-BLI configurations of a given airframe. Results indicate shaft power savings of 4.1% and 5.9% can be obtained for the boundary-layer ingesting TCT configuration of the CRM and TTBW, respectively. The present study also examines the coupling between airframe aerodynamics and the inlet flow distortion experienced by the TCT of a given aircraft configuration through airframe component sensitivity studies.

AATT↗
NASA NTRSDate not supplied

Effects of Aeroelasticity on Buffet Onset of Mach 0.8 Transonic Truss-Braced Wing

This paper presents a buffet simulation of the Mach 0.8 Transonic Truss-Braced Wing (TTBW) aeroelastic model using CFD solver FUN3D. A jig twist optimization is performed to obtain a flight optimized jig twist for the flexible Mach 0.8 TTBW model. A series of Delayed Detached Eddy Simulation (DDES) aeroelastic simulations has been conducted at Mach number 0.8 and altitude 40,000 ft using a structural damping of 2% to compare the pitch break prediction and the buffet behavior for the TTBW aeroelastic model. The unsteady pressure begins to grow at angle of attack of 4.0 ◦ , which might indicate the buffet onset, and rises one order of magnitude larger at angle of attack of 4.5 ◦ . In contrast, the buffet onset for the TTBW 1g model appears to be at the angle of attack of about 3.5 ◦ . The delay in the buffet onset of the aeroelastic model is due to the load relief from the aeroelastic effect.

TTBW↗
NASA NTRSDate not supplied

Multidisciplinary Design Optimization of a Transonic Truss-Braced Wing using Physics-Based Models

Economic and environmental forces have placed pressure on the aviation industry to produce future aircraft designs with substantial improvements over those flying today. In order to meet these ambitious goals, new concepts such as the Transonic Truss-Braced Wing (TTBW) are being considered which diverge from the traditional tube-and-wing design. While this concept offers potential performance benefits over its traditional counterpart, it also features more coupling between various physics disciplines that must be considered during the design of the concept. This unique challenge provides a ripe opportunity for the application of multidisciplinary design optimization tool sets. The final work will couple together the mission analysis capability of Aviary with OpenAeroStruct for aerodynamic analysis and TACS for structural analysis. Using these tools we will preform a design optimization on the TTBW concept minimizing design fuel burn. The optimization will include design variables for mission trajectory, wing geometry, and structural sizing variables.

mbsae↗
NASA NTRSDate not supplied

Quantification of Design Trade-Offs When Comparing Transonic Truss-Braced Wing to Advanced Tube and Wing Aircraft

Interest in novel aircraft configurations has continued to grow in response to increasing demand for improved fuel efficiency. One such configuration of interest is the Transonic Truss-Braced Wing (TTBW). Because the improvement of the TTBW comes from increased efficiency during cruise, it offers increasing returns as the mission distance increases. As a result, there is often a crossover point which represents the minimum mission range where the TTBW will offer a fuel burn reduction relative to a similar Tube and Wing aircraft with similar component technology levels. Aircraft rarely fly missions at their maximum range, so it is important to investigate not only the maximum benefit, but also the most likely benefit. Design decisions and analysis assumptions that significantly impact this crossover point include whether to put fuel in body tanks, how weight build-up estimation is calibrated, engine technology selection, and flight Mach number. This study, conducted under NASA’s Sustainable Flight Demonstration project and inspired by differing assumptions made by different research teams, details the impacts of changing these design decisions and assumptions.

Carl J Recine↗
NASA NTRSDate not supplied

Quantification of Design Trade-Offs When Comparing Transonic Truss-Braced Wing to Advanced Tube and Wing Aircraft

Interest in novel aircraft configurations has continued to grow in response to increasing demand for improved fuel efficiency. One such configuration of interest is the Transonic Truss-Braced Wing (TTBW). Because the improvement of the TTBW comes from increased efficiency during cruise, it offers increasing returns as the mission distance increases. As a result, there is often a crossover point which represents the minimum mission range where the TTBW will offer a fuel burn reduction relative to a similar Tube and Wing aircraft with similar component technology levels. Aircraft rarely fly missions at their maximum range, so it is important to investigate not only the maximum benefit, but also the most likely benefit. Design decisions and analysis assumptions that significantly impact this crossover point include whether to put fuel in body tanks, how weight build-up estimation is calibrated, engine technology selection, and flight Mach number. This study, conducted under NASA’s Sustainable Flight Demonstration project and inspired by differing assumptions made by different research teams, details the impacts of changing these design decisions and assumptions.

Carl J Recine↗
NASA NTRS2002

External merology truss technology demonstration (KITE)

To achieve micro-arcsecond astrometry, SIM's external metrology system must track the relative changes of three baseline vectors with a precision of tens of picometers over a one-hour time scale.

metrology interferometry corner cube truss picomet↗